Antenna circuit



Nov. 1G, 1931.

H.v N. MISENHEIMER ANTENNA CIRCUIT Filed July 19, 1928 L Z4 J/gr .9, Il, Al* l L *E zyLsZ/utter ZZ kl, v JZ] 5122 Z4 Z5 f t? 12 /V i Y' [4 *E unsTmtr Z6 |Z2 123i INVENTOR I YT/l Mise/@MWF ATTORNEY Patented Nov. 10, 1931 UNITED STATES PATENTL OFFICE .i

HARVEY N. MISENHEIMER, or BRooKLYN, NEW Yonx, nssrGNon 'rov AMERICAN 'rra-ia.

PHONE AND TELEGRAPH COMPANY, A Ycon-PQRATION orNEW vom: Y

ANTENNA CIRCUIT Application filed July 19, 1928. Serial No. 293,887.

This invention relates to transmitters for radio and high frequency currents and to antenna circuits therefor.

In this application there will be described a method for limiting the current in the output circuit of a radio or high frequency transmitter toy some definite or predetermined value without limiting or substantially affecting the. current delivered to the antenna m or antenna circuit, or circuits, coupled or otherwise connected to the transmitter.

It is frequently desirable to increase the power of a radio or high frequency transmitter to such an extent as to necessitate a replacement of the coils, condensersresist ances, if there be any, and/ or meters or measuring or indicating devices in the station portion of the antenna feed circuit, such a replacement being deemed essential when any 2o of the above enumerated elements cannot conveniently carry the increased current. LThe method and arrangements to be described hereinafter permit an increase in the power of the transmitter to be madewithout changing or replacing any of these elements. The

' method and arrangements are useful whenever the transmitter is used, at certain times, on a convenient low power, and at certain other times, on a substantially higher power,

or powers because it will permit the employment of elements of low current capacity and the meters or other indicating devices may, if desired, give full scale readings or indications of they current magnitude for all powers. The method and arrangements of this invention'have been found particularly useful with the well-known multiple tuned antenna, for the adjustmentof the antenna feed ratio to the power used may be easily 40 made by operating asingle switch or its equivalent, preferably located within the building housing the transmitter and, therefore, this adjustment need not be madel by changing the down lead tuning coils at six or so widely distant points along the antenna.

The primary feature of this invention resides in the employment of an inductance so arranged as tov shunt some or all of the above mentioned coils, condensers, resist-y ances, meters, etc. connected in theA station portion of the antenna feed circuit,A this inductance thereby Klimiting the current flow-K' ing therethrough to some definite Vand predetermined value. The use of this shunt in ductance has alreadybeen successfully em-v ployed in various forms of antenna circuitsk and has resulted in considerable economy and efficiency. i 1

lVhile this invention will be pointed out with particularity in thev appended claims, the invention both as to its further objectsand features will bebetter understood from the detailed description hereinafter following when read in connection Vwith the accompanying drawings in which Figure 1 shows an arrangement interconnecting an antenna with a transmitter, an inductance' being arranged to shunt those elements in the antennaf feed circuit which are not to carry current of an amplitude greaterthan some predetermined value, and Fig. 2 shows a generalization of the arrangement shown .in Fig. 1.

In Fig. 1 of the drawings there is shown a transmitter Ty which may be any well known form Aof radio orhigh frequency transmitter. Transmitter T may, for 1.n'-

stance, include an oscillator capable of sus# taining oscillations of any one of a number of dierent frequencies, coupled to a source of signalsand an `amplifier having one or more stages of amplification in order that any desired power level may beV obtained. Transmitter T may be terminated by a tuned circuit as shown in Fig. 1, this tuned circuit including a winding L1, Vwhich may be adjustable in thev magnitude vof itsinductance, a winding L2 and a condenserC of variable ca pacity in shunt with windings Li andL2. Accordingly, upon adjustment of the inductance of winding L1 and of the capacity of condenser C, the tuned circuit may be brought into resonance at any desired frequency.

The winding L2 of the latter tuned circuit is shown coupled to a winding L3. Winding L3 is connected in series with another winding L, of variable inductance, an ammeter A or other indicating device, and an antenna N, winding L3 being also connected to ground. It will be apparent that the resonant period of the circuit in series with winding L3 may be brought to any desired value by changing the magnitude of the inductance of winding L5.

A single'pole, single-throw switch S is in series with a winding L5 which is also of variable inductance as shown. Switch S may be manipulated to connect winding L5 in shunt across the series circuit including winding L3, winding L4 and ammeter A. Winding L5 is the inductance of this invention used to shunt windings L3, L3 and meter A to prevent excessive currents from flowing through the latter elements and this represents one of the novel features of the invention.

When the transmitter T'is impressing a particular frequency upon the antenna N. a voltage E may be considered to act in series with the branch including winding L3. Then if the shunt coi-l L5 is not connected to the circuit and if the circuit is brought to rresonance atthe frequency of transmitter T by the adjustment of the inductance of wind` ing L5, the inductive reactance in the circuit will be equal to the capacitative rcactance, or

X1 Vbeing the reactance component of impedance Z1, X2 the reactance component of impedance Z2 and X3 the reactance component of impedance Z3. These relations may be more accurately written mathematically. as follows:

Nowlet switch S be manipulated so as to connect the coil L5 in shunt with coil L3, coil L4 and ammeter A. Coil L4 may then be changed in the magnitude of its inductance to cause the circuit to be in resonance at the same frequency as heretofore. Hence,

In this connection, it is to be noted that the resistance components of the impedances Zl and Z5 are very small when compared with the reactance components and may, therefore, be neglected.

Since coils L3 and L4 are in series relation- Since is equal to the true antenna current, or IB,

the current through ammeter A, or IA, and 3.

the current in the shunt coil L5, or IS, then L=IA+IS ,(6)

Equation clearly states that the true antenna feed current IB is equal to the sum of the station feed current IA and the shunt coil current TS. It willbe apparent that by employing this shunt coil, the true antenna feed current,.i. e., the current supplied to antenna N, is divided between two branches, one including coils L5, L, and ammeter A and the other including shunt coil L5. If the transmitter T is used to supply power in excess of some predetermined value, vthe shunt coil may be connected as shown toprevent excessive current from iiowing through coils L3 and L3 and ammeter A. If transmitter T is employed to transmit different power levels in excess of some predetermined value, then coil L5 may be set at corresponding values of inductance in order that the current iiowing through the circuit including coil L3, ,coil L.L and ammeter A may not exceed some predetermined value. Thus', it becomes unnecessary to replace coils L3 or L4 or ammeter A as the power output of transmitter T is in creased to very great levels.

Equation (5) may be written Vas follows:

tween the reactance of the shunt coil circuit and the reactance of the station feed circuit,

the currents in the respective branches may be brought to any desired ratio.

iii)

In Fig. 2, the transmitter T' is coupled to` the antenna N through a T-type network. Here impedances Z4, Z5 and Z5 are shown generally, impedances Z4 and Z5 being con` nected in seriesrelationship between transmitter T and antenna N, and impedance Z5 being connected across transmitter' T from the point of contact of impedances ZLAL and Z5. In other respects, elements similar to those in Fig. l are designated by similar reference characters.

If the antenna circuit of the arrangement of Fig. 2 need be tun-ed to the frequency of the current transmitted by transmitter T by means of a series condenser, such a condenser may be located near the antenna and it will be clearly understood that this condenser may be variable so that its capacitative reactance may be changed to any desired value. The capacitative reactance of this condenser, if used, will now be included in impedance Z5, impedance ,Z5 equaling R3ljX5- In the arrangement shown. reactance X1 will always Vbe inductive in effect. Also, when considering the changes produced by the addition of shunt Vcoil L5, the resistance component of impedance Z1, i. e., R1, may Vbe neglected in practice. The ratio of the total antenna current IB to the station feed current IA may then be determined by measurement for all frequencies which are to be employed in transmission. For any particular frequency, the true antenna feed current IB will be equal to the station feed current IA multiplied by a constant, or

There. will be a different constant for each frequency. Y

It will be understood that the arrangementv of Fig. 2 is a generalized circuit showing how shunt coil L5 may be applied in practice to any transmitting circuit and that variations from that arrangement may be employed in practice without departing from the spirit and scope of the invention. n Vhile this invention has been shown in a Vter to said antenna circuit.

2. The combination of a transmitter of radio frequency current, an antenna circuit, a first circuit including inductance of predetermined magnitude, said first circuit being connected in series with said antenna circuit and being coupled to said transmitter, and a second circuit including inductance of predetermined magnitude and switchin means for connecting said second circuit 1n shunt with the first circuit, the inductances of the first and second circuits being of magnitudes inversely proportional to the currents which shall flow thereover. f

3. The combination of an antena, a first inductance, an ammeter, said antenna, said first inductance and said ammeter being con-V nected in series relationship, said first inductance and said ammeter conveniently carrying current of an amplitude less than a predetermined value, a second inductance, a switch for connecting said second inductance so as to shunt said first inductance and said ammeter when current is to be supplied tov particular arrangement merely for the purpose of illustration, it will be clearly understood that the general principles of this invention may be applied to other and widelyr varied organizations Without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is: 1. The combination of a transmitter, an antenna circuit, a winding having a predetermined inductance connected in series in l 

